Modularly structured digital communications systems serve the purpose of connecting terminal equipment usually having versatile performance features to one another and for connecting such terminal equipment to communications networks, particularly public networks. A special edition of "telcom report", ISDN in Buero, 1985, discloses such a communications system to which analog and digital telephones, telecopiers, multi-functional terminals, work stations, personal computers, teletex, screen text stations and data terminal equipment can be connected. The structure of the system is designed such that traditional devices having analog transmission can also be connected in addition to digital terminals, as well as, a networking with other communications systems. The essential component part of this communication system is a central communication computer having a system data base and at least one multi-tasking operating system. A "task" is herein defined as an independent execution unit that is composed of a runnable program as well as of its respective executive environment, for example memory occupation or apparatus allocation. At every point in time, each task has the status of "active", "waiting" or "quiescent". Tasks can be executed in parallel to one another by a multi-tasking operating system, whereby this can be performed both by means of a plurality of processors working independently of one another as well as by a single processor in a time-division multiplex method. Further critical properties of tasks are that they can communicate with one another by status reports and can mutually synchronize with one another.
The performance capability of such a digital communications system is critically determined by the software structure of the system. A known prior art communications system has a modularly structured software architecture whose critical component parts are, first, the multi-tasking operating system or the data base and, second, the actual switching software composed of the periphery software, of the line-technology software and of the exchange-oriented connecting software. The allocation of sub-functions of the control software to individual software modules or the overall software structure of the known communications system are adapted to the system size of several hundred through several thousand connections.
The performance and the usefulness of such a communications system are critically dependent on the ability to organize and maintain the system that, in addition to other aspects, are subsumed under the term operating technology. The organizability of the system should be able to handle individual user requests with respect to system expansion, numbering plan, device and communications service multiplicity in a fast simple reliable and user-friendly way. The most important functions of maintenance are, for example, manual switch requests for inhibiting, unlocking and switching system units, manual check requests, execution tracking and diagnosis acquisition as well as providing clear-text output for the system operator. The prerequisite for the organizability and maintainability of the system is an all-encompassing "administration" of the communications system. Included in this "administration" are data storage generation and regeneration, storing and maintaining the customer data for system configuration, communications services and terminal equipment as well as traffic measurements.